Air pollution is one of New York City’s most significant public health challenges.  More than 300,000 children have been diagnosed with asthma in the City. Eliminating the use of heavy heating oil is the highest-impact step we can take to reduce air pollution and advance PlaNYC's goal of making New York City’s air the cleanest of any major U.S. city.

What is Heavy Oil?

There are three grades of heating oil burned in New York City, No.’s 6, 4, and ultra-low sulfur 2 (ULS 2). The heaviest grade, No. 6 oil, resembles tar or asphalt. It is often referred to as residual oil because it literally comes from “the bottom of the barrel” of the petroleum refinement process. To maintain a liquid form, No. 6 oil must be heated to at least 110 degrees Fahrenheit.  

Pictured are vials of ULS 2, No. 4, and No 6 heating oil. Each vial was one third full and was shaken before photographing. Note that ULS 2 heating oil is dyed red

No. 6 oil and the less-viscous No. 4 oil can contain sulfur, nickel, and other impurities and can be difficult to burn cleanly and completely. During combustion, unburned fuel creates soot, some of which spews out of the chimney and the rest of which coats the boiler heat exchange surfaces – as seen in the images below.  

This soot acts like insulation and drastically reduces the efficiency of the boiler. Daily equipment cleaning is needed during periods of high use to maintain boiler operating efficiency. 

The image on the left shows sludge buildup on the burner air spinner and the combustion chamber floor. The image on the right shows soot that has been scraped out of the boiler tubes during cleaning. Photo Credit:Tom Sahagian

What are the health impacts of burning heavy oil?

Because of its high sulfur content, burning No. 6 oil releases significant quantities of fine particulate matter (PM2.5) in chimney exhaust. When PM2.5 becomes embedded in people’s lungs it can aggravate existing respiratory diseases such as asthma and cause heart attacks or other cardiovascular episodes. Emissions of the heavy metal nickel are also a major concern, as it can increase the risk of heart disease and other ailments when ingested.

Map showing wintertime ground-level PM2.5 concentrations—as measured by the NYC Department of Health and Mental Hygiene at 150 monitoring sites across the City – overlaid with the locations of buildings that burn No. 6 oil. Picture Credit:DOHMH

What are the health benefits of using cleaner fuels?

Eliminating the use of heavy oil and transitioning to the cleanest fuels will have dramatic health benefits.  By achieving the NYC Clean Heat goal of reducing PM2.5 by 50% over the next two years, we will save 120 lives a year, prevent 200 emergency room visits and 77 hospitalizations, and save the health care system $3.9 million each year.